Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$172.75	4.113%	$179.8552	$179.86	$179.85	$179.90
Purchase #2	$124.43	3.601%	$128.9107	$128.91	$128.90	$128.90
Purchase #3	$202.82	5.669%	$214.3179	$214.32	$214.30	$214.30
Purchase #4	$166.51	3.364%	$172.1114	$172.11	$172.10	$172.10
Purchase #5	$152.57	13.841%	$173.6872	$173.69	$173.70	$173.70
Purchase #6	$179.97	5.837%	$190.4748	$190.47	$190.45	$190.50
Purchase #7	$250.89	3.195%	$258.9059	$258.91	$258.90	$258.90
7 purchase totals =	$1,249.94		$1,318.2631	$1,318.27	$1,318.20	$1,318.30